Division of Communication and Auditory Neuroscience, House Research Institute, 2100 West Third Street, Los Angeles, California 90057, USA.
J Acoust Soc Am. 2011 May;129(5):3123-33. doi: 10.1121/1.3573992.
Distortion product otoacoustic emissions (DPOAEs) measured in the ear canal represent the vector sum of components produced at two regions of the basilar membrane by distinct cochlear mechanisms. In this study, the effect of stimulus level on the 2f(1) - f(2) DPOAE phase was evaluated in 22 adult subjects across a three-octave range. Level effects were examined for the mixed DPOAE signal measured in the ear canal and after unmixing components to assess level effects individually on the distortion (generated at the f(1), f(2) overlap) and reflection (at f(dp)) sources. Results show that ear canal DPOAE phase slope becomes steeper with decreasing level; however, component analysis further explicates this result, indicating that interference between DPOAE components (rather than a shift in mechanics related to distortion generation) drives the level dependence of DPOAE phase measured in the ear canal. The relative contribution from the reflection source increased with decreasing level, producing more component interference and, at times, a reflection-dominated response at the lowest stimulus levels. These results have implications for the use of DPOAE phase to study cochlear mechanics and for the potential application of DPOAE phase for clinical purposes.
耳声发射的失真产物（DPOAE）在耳道中测量的结果代表了基底膜两个区域由不同耳蜗机制产生的分量的矢量和。在这项研究中，我们在三个倍频程范围内评估了刺激水平对 2f(1) - f(2) DPOAE 相位的影响。对在耳道中测量的混合 DPOAE 信号和去混合成分后评估单个成分的水平效应，以分别评估失真（在 f(1)、f(2)重叠处产生）和反射（在 f(dp)处）源的水平效应。结果表明，随着刺激水平的降低，耳道 DPOAE 相位斜率变得更陡；然而，成分分析进一步解释了这一结果，表明 DPOAE 成分之间的干扰（而不是与失真产生相关的力学变化）导致了在耳道中测量的 DPOAE 相位的水平依赖性。随着刺激水平的降低，反射源的相对贡献增加，产生更多的成分干扰，有时在最低刺激水平下产生以反射为主的反应。这些结果对使用 DPOAE 相位研究耳蜗力学以及将 DPOAE 相位潜在应用于临床目的具有重要意义。
